Problem: Simplify the following expression: $k = \dfrac{4r^2 + r}{pr} - \dfrac{6pr - r^2}{pr}$ You can assume $p,q,r \neq 0$.
Answer: Since the expressions have the same denominator we simply combine the numerators: $k = \dfrac{4r^2 + r - (6pr - r^2)}{pr}$ $k = \dfrac{5r^2 + r - 6pr}{pr}$ The numerator and denominator have a common factor of $r$, so we can simplify $k = \dfrac{5r + 1 - 6p}{p}$